Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
  • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
  • C07C5/2767—Changing the number of side-chains
  • C07C5/277—Catalytic processes
  • C07C5/2772—Catalytic processes with metal oxides

Definitions

• This invention relates to the preparation of the skeletal isomerization catalyst which permits the isomerization of normal olefins to their isomers. Specifically, this invention relates to the skeletal isomerization as well as double bond isomerization of four to twenty carbon-numbers olefin. This invention more particularly relates to the conversion of linear alkenes into the branched alkenes having the same carbon numbers.
• the catalyst in this invention is prepared by impregnation process, then the calcination and activation steps, to form a composition of the catalyst named as SKISO-ll, an oxide of Group IIIA on the active alumina pellet.
• the double-bond isomerization reaction of olefin often occurs in the presence of acidic catalyst by proton transfer between olefins. However, it is not necessary to proceed the reaction at high temperture. Skeletal isomerization of olefins is known to be conducted by contacting unbranched olefins with acidic catalysts at more extreme conditions. Therefore, for skeletal isomerization of olefin, the alkyl carbonium ion which is the transition state of double-bond isomerization reaction needs to undergo a rearrangement, and subsequently a proton transfer step to form the desired products.
• the skeletal isomerization catalyst were mostly prepared from the alumina support with some modifications on the surface by halogen-containing compounds, such as HBr or butyl bromide. Examples are : Sun United States Pat. 4,778,943, issued 18 Oct 1988; Sun United States Pat. 4,654,463, issued 31 Mar 1987; and Eleazar et al. United States Pat. 4,433,191, issued 21 Feb 1984.
• the catalyst in this invention is prepared without any modification of halide compound on the catalyst surface and can be employed to the skeletal isomerization of olefins effectively.
• the product of skeletal isomerization for C 4 olefin is isobutylene which is one of the feedstock for producing methyl tertiary butyl ether (MTBE), an ether compound with high octane number used in gasoline pool.
• the desired product is isoamylene which is the feedstock of producing tertiary amyl methyl ether (TAME), also a high octane number compound.
• TAME tertiary amyl methyl ether
• Normal olefins are converted into iso-olefins in the presence of the SKISO-ll catalyst of this invention.
• the support used in the catalyst is any crystalline type of aluminas, preferred eta- or gamma- alumina with the surface area of above 40 to about 500 m 2 /gram (as measured by the BET method using N 2 ).
• Other inorganic oxides may be used in the catalyst of this invention.
• the catalyst of this invention should contain at least 60 mole % of alumina. Examples of other inorganic oxides which can be used along with alumina are magnasium oxide, calcium oxide, phosphorus oxide, tungsten oxide and palladium.
• the catalyst should contain an oxide of Group IIIA from about 0.01 to about 20 wt %, preferably from 0.3 to about 11 wt %, based on the total catalyst weight.
• the preparative method for the catalyst as well as the application of the catalyst on the skeletal isomerization of normal olefins and the resulting mixture are disclosed in this invention.
• the catalyst of this invention can be utilized in the skeletal isomerization of olefins to convert n-butenes into isobutylene or to convert n-pentenes into isoamylenes, within which the reaction can be double bond or skeletal isomerization.
• the isomerization reaction of olefins is well known to be limited by the thermodynamical equilibrium of reacting species.
• the skeletal isomerization catalysts described in some patents or published papers were mostly prepared from the treatment of halogen-containing compound in order to maintain the activity and the selectivity. Hence, there are some disadvantages for those catalysts, such as the investment of the facilities too high, the treatment of the process waste too difficult, etc.
• the objective of this invention is to propose a new catalyst for which the cost of the process investment can be reduced and the skeletal isomerization of normal olefins can easily proceed.
• the characteristics of the preparation process for the catalyst are :
• the feedstock of skeletal isomerization contains at least one alkene, preferably an alkene having from 4 to 8 carbon numbers per molecule.
• the alkene may have internal or terminal double bonds.
• the normal alkenes may contain other hydrocarbons having the same numbers of carbon atoms, such as alkanes.
• Particular feedstocks in this invention are fractions containing butenes, or mixtures of butenes with isobutylene, mixtures of pentenes with isoamylenes. Such fractions are commonly produced in petroleum refineries or petrochemical plants, for example, C 5 stream from naphtha crackers and C 4 stream from MTBE plant.
• the olefinic feedstocks can contain inert diluents with the content of alkenes in the range of above 10 to 95 wt % of the feed stream.
• the typical example of the application of the catalyst is on the isomerization reactions, either double bond or skeletal isomerization, of the C 4 or C 5 olefins.
• C 4 olefin refers to the follow olefins: 1-butene, cis-2-butene, trans-2-butene and isobutylene.
• C 5 olefin refers to the following olefins : 1-pentene, cis-2-pentene, trans-2-pentene, 3-methyl-1-butene, 2-methyl-1-butene and 2-methyl-2-butene.
• the catalyst is regenerable by heating in an oxygen and nitrogen-containing gas at the temperature in the range of above 300 o C to about 800 o C.
• a hydrogen or nitrogen gas is incorporated in the reacting mixture with a molar ratio of gas to the reacting mixture of zero to about ten, preferably a molar ratio of zero to 3.
• the said catalyst is placed in a fixed-bed reactor which has the inner diameter of 2.54 cm and the length of 30.5 cm. Some inert solid particles are placed in lower and upper ends of the reactor to support the catalyst and to make uniform distributions of the reacting stream within the reactor.
• the experimental apparatus also includes feed pump, heating medium, product collecting and sampling units, mass flow meter and temperature-controlled system, etc. The product is analyzed by gas chromatography, a Carlo Erba GC 6000 Vega Series unit with FID detector.
• the column is a capillary type.
• isoamylenes 7.8 wt% of pentane and C 4 - and 8.9 wt% of C 6 + hydrocarbons.
• the conversion of n-pentene and the selectivity of isoamylene were estimated as 0.804 and 0.836, respectively. If pentenes in the product is normalized and compared with the equilibrium compositions of C 5 olefins which are estimated thermodynamically, a consistent result is obtained and shown in Table I.
• the feed is a mixture of 94.25 wt% of 2-pentene and 1.29 wt% of isoamylenes with the flow rate of 35 ml/min.
• the amount of the catalyst used is 5.5 grams.
• the operating conditions are at one atmosphere and different temperature, such as 200, 250, 300, 350, 400 and 450 o C.
• the results show that the conversion of normal pentene and the selectivity of isoamylene are similar within the temperature range of 300 to 400 o C.
• the composition of product for each condition is shown in Table III.
• the feed is 99.5 wt% of 1-butene with the flow rate of 100 ml/min.
• the operating conditions were selected as at one atmosphere and WHSV at 1.0 for different temperature, 250, 300, 350, 400 and 500 o C.
• the yield of isobutylene is different for various temperature. A quick increasing of the yield of isobutylene is occurred up to 400 o C reaction temperature.
• the composition of product for each condition is shown in Table IV.
• the calcination temperature of the catalyst also affects the activity of the catalyst on the skeletal isomerization due to effects on the properties of the catalyst, such as surface area and the distribution of active sites.
• the experimental procedure was the same as case II except that the weight hourly space velocity is at 2.5. The results are summarized in Table V.
• the yield of isobutylene for each calcination temperature depicts that a better choice of the calcination temperature of the catalyst is located at 500 o C up.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (2)

• 1991
  • 1991-04-09 EP EP19910303113 patent/EP0508008B1/fr not_active Expired - Lifetime
  • 1991-04-09 DE DE1991621695 patent/DE69121695T2/de not_active Expired - Fee Related

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